Artificial cornea based on a polymer with high water-absorbent properties

Damage to the cornea has led to loss of eyesight in thousands across the globe. Though corneal transplantation is the therapy of choice for many, the problem of scarce donor material persists. Also, a sub-group of patients do not tolerate transplanted corneas. This has necessitated application of an alternative means of restoring eye sight. Next generation biomaterials have been utilized to create an artificial cornea for the blind. The Fraunhofer team created the ArtCornea by adding a novel surface coating to the base polymer material to ensure anchorage in host tissue and functionality of the optic. Based on a polymer with high water-absorbent properties, the device is designed to help patients whose cornea has become clouded, as well as those not who would not tolerate a donor cornea. The haptic edge was chemically altered to encourage local cell growth. These cells then graft to the surrounding human tissue, which is essential for anchorage of the device in the host tissue. "A great many patients suffering from a range of conditions will be able to benefit from our new implant," said project manager Dr Joachim Storsberg, from the Fraunhofer Institute for Applied Polymer Research. The researchers aimed to enlarge the optical surface area of the implant in order to improve light penetration beyond what had previously been possible. "Once ArtCornea is in place, it is hardly visible, except perhaps for a few stitches," noted Dr Storsberg. "It's also easy to implant and doesn't provoke any immune response."

The researchers have also made a chemically and biologically inert base material biologically compatible for another artificial cornea called the ACTO-TexKpro. They achieved this by selectively altering the base material, polyvinylidene difluoride, by coating the fluoride synthetic tissue with a reactive molecule. This is said to allow the patient's cornea to bond together naturally with the edge of the implant, while the implant's inner optics, made of silicon, remain free of cells and clear. Both artificial retinas have been tested in vivo in several rabbits. The researchers reported that after a six month healing process, the implanted prostheses were accepted without irritation and securely anchored within the eye. Further trials are now underway.

An earlier discovery for treating blinding cornea disease was the Boston keratoprosthesis (artificial corneas). The Boston keratoprosthesis is a collar button shaped device consisting of a PMMA [poly(methyl metacrylate)] optic that clamps within it a donor ring of corneal tissue and is stitched in place into the recipient eye. It creates a very clear window through which patients can see clearly. It has many advantages and benefits over conventional corneal transplants and other cornea surgeries, such as patients can benefit from good long-term vision, because it eliminates the problem of graft rejection and failure and visual recovery is much faster than conventional corneal transplants. This procedure eliminates the need for systemic immuno-suppression and steroids, which means less harm to the body and reversible and may be easily repeated. There is less irregularity and astigmatism, meaning lower spectacle correction required.